The most diverse loading devices for goods vehicles are known. They can be attached to a self-propelled goods vehicles, trailers or other goods vehicles with a fixed loading platform, with a fixed superstructure or they can also be attached to vehicles with interchangeable superstructures. They can also be attached to the vehicle superstructure itself, which can be interchangeable, for example for semi-trailer vehicles. Such devices are advantageously attached so that the lifting platform when raised adjoins the rear edge of the loading surface. However, the loading devices can also be attached laterally at the side of the vehicle or superstructure.
Numerous efforts have been made to achieve advantageous kinematic conditions. The designs were however adapted to the prevailing requirements, depending on whether the lifting platform can be pivoted into the vertical position to function as a tail gate or side wall, or depending on whether special angular conditions are desired. Some tests have also been made with combination systems. In a loading device system disclosed by the German Offenlegungsschrift No. 22 53 654, the ends adjoining the lifting platform of two piston-cylinder rams both act at a distance from the pivoting axis on the lifting platform so that the latter can be upwardly pivoted. With a construction of this kind there is a risk of the outer end of the lifting platform tilting upwards instead of moving up and down as a horizontal surface. Special steps must be taken to counter such tilting. Furthermore, in the region of the pivoting means, which are fixed to the vehicle, this construction is provided with an intermediate link which bears at different places of the support system and/or of the parallelogram links, depending on its particular construction. This results in particularly complicated conditions which can hardly be controlled, owing to the unstable position of the intermediate links which must be multi-jointed. In one solution to the problem in which one side of the intermediate link is hinged to the vehicle and the other is fixedly supported on the vehicle, all joint axes at the support system end are situated in one plane, a feature which does not allow optimum kinematic conditions to be obtained.
In view of the many different types of vehicles and due to the different requirements made thereon, it is necessary for loading devices to fulfill the most diverse functions and to perform widely different movements and, in view of the need for being operated by only one person, for example the driver, they must be constructed in their entirety as advantageously as possible to comply with safety regulations and to ensure efficiency. This gives rise to many problems which can be solved on the one hand mechanically and on the other hand hydraulically, and it is necessary to judge whether a kinematic solution or a hydraulic solution is to be given perference for reasons of operation, costs or safety.